Pressure & flow in arteries & veins Flashcards
what is systolic pressure
it is the blood pressure when the heart is contracting
what is systolic pressure specifically
the maximum arterial pressure during contraction of the left ventricle of the heart
what is systole
the time at which ventricular contraction occurs
what is diastolic pressure
it is specifically the minimum arterial pressure during the relaxation and dilation of the ventricles of the heart when the ventricle fill with blood
what is pulse pressure
the difference between the systolic pressure and diastolic pressure
what is pulse pressure measured in
mmHg
millimetres of mercury
what does the pulse pressure represent
the force that the heart generates each time it contracts
what is resting normal blood pressure
120/80mmHg, then the pulse pressure is 40mmHg
what are Korotkoff sounds
arterial sounds heard though a stethoscope applied to the brachial artery distal to the cuff of a sphygmomanometer that change with varying cuff pressure
what are Korotkoff sounds used for
determination of systolic and diastolic blood pressure
what is hearing kormokoff sounds used as a common method for
noninvasive measurement of blood pressure in adults
when is systolic blood pressure taken in relation to listening to korotkoff sounds
it is taken to be the pressure at which the first korotkoff sound is heard
what makes up the vascular tree
arteries, arterioles, capillaries, venules and veins
during the ejection phase what are the ventricles doing
contracting and pushing the blood out of the aortic valve
describe the maintenance of pressure in arteries during the ejection phase
- push of blood out the aortic valve
- elastic walls of the aorta swell
- the swelling absorbs energy
describe pressure in relation to the aorta
the aorta is an elastic artery
it damps down pressure
it controls pressure varyingly
this artery stops pressure getting too high or too low during diastole
describe the maintenance of pressure in arteries during the relaxation phase
ventricles fill
the aortic valve is shut
the elastic energy is released from the walls of the aorta
maintaining the pressure
in systemic circulation, what is the pressure wave affected by
stroke volume
velocity of ejection
elasticity of arteries
total peripheral resistance
what is normal arterial pressure equal to
120/80mmHg
interns of systemic circulation, what is the relationship of pressure and the vascular tree
pressure falls throughout the vascular tree
what is pressure like through arteries
small pressure, low pressure
what is pressure like through the arterioles
pressure is greater as arterioles are resistance vessels
what is pressure like through capillaries
pressure is already low when blood gets to the capillaries - this is good as capillaries are thin-walled
what is the systemic filling pressure
the very small pressure gradient that is left to push blood back through the veins
what must total flow through your arteries, arterioles, capillaries, venules and veins be
it must all be the same
what must the velocity of blood flow be through arteries, arterioles, capillaries, venules and veins
it is not all the same
velocity changes in each of the vessels
what does the velocity in blood vessels relate to
the total cross sectional area of the particular blood vessel
what does the velocity of blood flow depend on
the total cross sectional area of vessels
describe total cross sectional area of the aorta
the aorta has a big diameter
however there is only one aorta
therefore the total cross sectional area is very small
describe the total cross sectional area of capillary vessels
capillaries have small diameters, tiny in fact
however there are thousands of capillaries
which makes the total cross sectional area large
5000cm squared in fact
describe blood flow through different total cross sectional areas
blood flow is fastest through the aorta due to the aorta having a small total cross sectional area
blood flow is the slowest through the capillaries as the capillary vessels have the greatest total cross sectional area
when does blood flow speed up again following it flowing through the capillaries
blood flow speeds up again going through the vena cava
describe the pressure in veins
the pressure is low
there is a small pressure gradient pushing the blood from the venules to the veins to the heart
20mmHg
describe why the pressure in the veins may be so small
because these vessels are thin walled, there is not much smooth muscle, therefore these vessels collapse and are distensible very easily, these vessels are very susceptible to external influences
state 5 things that affect venous pressure and venous return
gravity the skeletal muscle pump the respiratory pump venomotor tone systemic filling pressure
does gravity affect the driving pressure from arteries to the veins
no
does gravity make it more difficult for the blood to get back to the heart
no
what can gravity cause
venous distention in the legs and venous collapse in the neck
describe the result of gravity causing venous retention in the legs
reduced end diastolic volume decreased preload weaker contraction reduced stroke volume reduced cardiac output reduced mean arterial pressure result in orthostatic hypotension
what is the result in gravity causing venous collapse in the neck
your central venous pressure can resultantly be estimated
what is the skeletal muscle pump
it is a collection of skeletal muscles that aid the heart in circulation of the blood
what is the importance of the skeletal muscle pump
it is important in increasing venous return to the heart
it plays an important role in arterial blood flow
what is the role of peripheral vein valves
they stop the blood going backwards, pushing the blood towards the heart
describe the effect on veins from the constriction of skeletal muscles
the squeeze capacitance of blood that is in the veins in the skeletal muscle back towards the heart, increasing venous return
what does the skeletal muscle pump’s effect on the veins have significance for
rhythmic exercise
static exercise
hot guardsmen - not using pump
deep vein thrombosis varicose veins
how is sustained contraction of skeletal muscle not good
it stops blood getting through the veins back to the heart
describe how the respiratory pump effects the blood flow through veins
the faster you breathe in the deeper you breathe in the more you encourage venous return the more blood back to the heart increase in your end diastolic volume think about exercise
the respiratory pump is one of the things that maintains end diastolic volume
describe how inhalation effects venous return
inspirations tends to draw blood back to the heart
inhalation increases venous return
describe how venomotor tone effects the blood flow through veins
activation of smooth muscle around the veins squeezes the blood towards the heart
venomotor tone mobiles the capacitance of veins
the squeeze of the smooth muscle pushes the blood back to the heart, increasing end diastolic volume
what is venomotor tone
is is a state of contraction of the smooth muscle surrounding the venules and veins
describe venomotor tone
it is the degree of tension in the muscle coat of a vein that determines the shape of the vein
what is result of changes in venomotor tone
the capacity of veins is altered
state 3 things that help maintain/increase end diastolic volume
the skeletal muscle pump
the respiratory pump
venomotor tone
what is the major thing that is driving blood through your venules and veins to the heart?
your systemic filling pressure
what is arterial pressure measured by
Korotkoff sounds
what can estimated by jugular collapse
your central venous pressure
what does gravity cause
collapse of the jugular vein
